kje
100 W
On my way to build a 3s50p battery pack:
1) Charging: Open more than 150 18650 recycled laptop cells and charge them to 4.20V
2) Bleed down: Set for "bleed down" 4/5 months, then segregate cells determined by voltage
3) Capacity test: Discharge cells in pair with Imax B6 at 1A and write down capacity, then charging back to 4.20V
4) IR-test (Internal Resistance): Measure voltage using a multimeter before the Capacity test and after 20 seconds discharging at 1A, then you have the voltage drop: [unloaded V - loaded V = V drop]. Then use this formula to get the cells internal resistance: [V drop / Amp x 1000 = milli Ohms]
The Capacity test is a little time consuming and my Imax can`t discharge more than 1A. I hope the IR-test is proper. Most of the cells is discharged in pair but some as single cells, does that change the results? Give med some feedback please.
One example:
Cells that "bleed down" between 4.10V and 4.00V:
Best pair: 40mΩ and 4458mAh
Worst pair: 240mΩ and 1458mAh
1) Charging: Open more than 150 18650 recycled laptop cells and charge them to 4.20V
2) Bleed down: Set for "bleed down" 4/5 months, then segregate cells determined by voltage
3) Capacity test: Discharge cells in pair with Imax B6 at 1A and write down capacity, then charging back to 4.20V
4) IR-test (Internal Resistance): Measure voltage using a multimeter before the Capacity test and after 20 seconds discharging at 1A, then you have the voltage drop: [unloaded V - loaded V = V drop]. Then use this formula to get the cells internal resistance: [V drop / Amp x 1000 = milli Ohms]
The Capacity test is a little time consuming and my Imax can`t discharge more than 1A. I hope the IR-test is proper. Most of the cells is discharged in pair but some as single cells, does that change the results? Give med some feedback please.
One example:
Cells that "bleed down" between 4.10V and 4.00V:
Best pair: 40mΩ and 4458mAh
Worst pair: 240mΩ and 1458mAh